1. Field
This disclosure relates generally to device structures for high frequency signal transmission, and more specifically, to device structures for high frequency signal transmission having a ground plane.
2. Related Art
The frequency of high frequency device continues to increase which create issues not as significant prior to the increase in frequency. One example is the ground plane often used in high frequency circuits, and more specifically, in a microstrip transmission line which is used to transmit the high frequency signal to or from active circuitry. A solid ground plane is desirable but is not practical because of the need for chemical mechanical polishing (CMP) which is typically used in forming the ground plane. In order for the CMP to provide the desired function the ground plane cannot be solid but must have openings and these openings must be relatively large compared to the openings required just for interconnect. The degree to which the openings interfere with the desired functioning of the ground plane is related to the relationship between the wavelength and the size of the openings. Thus, with the openings being required to be of at least a particular size for proper CMP, an increase in frequency can reduce the effectiveness of the ground plane for that particular size.
Accordingly there is a need to improve upon one or more of the issues raised above.